Etching metal plates



No. 627,430. Patented lune 20, I899.

L. a LEVY. ETCHING METAL PLATES.

(Application filed firm as, 1899.)

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ETCHING METAL PLATES.

(Application filed Jan. 28, 1899.)

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WITNESSES UNITED STATES PATENT OFEIQE.

LOUIS E. LEVY, OFPHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO MAX LEVY, OFSAME PLACE.

ETCHING'METAL PLATES.

SPECIFICATION forming part of Letters Patent No. 627,430, dated June 20,1899. Application filed January 23, 1899; Serial No. 703,701. (Nomodel.)

To all whom, it may concern:

Be it known that I, LOUISE. LEVY, a citizen of the United States,residing at Philadelphia, in the county of Philadelphia and State ofPennsylvania, have invented new and useful Improvements in Processes ofand Apparatus for Etching Metal Plates, of which the following is aspecification.

This invention relates to a process of and apparatus for producingetched metal plates, more particularly such metal plates as are used inphotomechanical engraving or such branches of the art where metal platesare etched by acid or other liquid erodent to form in the plates lines,furrows, indentations, or striations for the production ofprinting-surfaces.

The object is, by the employment of a mordant, to produce aprinting-surface upon metal in which the indentations or lines producedas the result of the process are of a more perfect character than thoseproduced by the means ordinarily used; also, to reduce the cost ofproduction and obviate many of the objections incident to the processesand means heretofore employed.

The present invention includes an essentially new process of applyingthe mordant to a prepared plate, which mordant is projected and atomizedupon the plate to form therein, Where not protected by the resist andafter a certain depth is etched out, cupped or con cave indentations orlines. The carrying out of the process embodies the use of compressedair and ejector-nozzles for projecting the mordant in the form ofatomized spray upon a prepared metal surface, so that the mordant whichis projected thereon will drop therefrom Without flowing, the plate andatomizers being within a chamber or etching-box, so that the compressedair used to project the acid or mordant will be permitted to expand inthe chamber to reduce the temperature thereof and absorb the heat whichisgiven off by the chemical action of the erodent on the exposedportions of the plate. The chemical combination of the mordant with themetal is accelerated by the dynamic force of the tact.

rated with the metal base instantly upon con- This results in eroding orcutting away the metal in the direction of theimpact faster than thesame action proceeds laterally, so

that much or all of the required vertical depth may be etched before thelateral action of the mordant can materially affect the work. Moreover,the forcible impact of the atomized spray, besides accelerating thechemical combination of the mordant and the metallic base, preventsadhesion to the plate of bubbles of hydrogen gas andscum of metallicoXid which are developed by the chemical action and which in ordinarypractice. are removed by the workmen with a brush; also, by the use ofcompressed air for projecting the mordant the heat evolved by thechemical action of the mordant on the plate is absorbed by the expansionof the air in the chamber, thus keeping the chamber and the plate cool,so thata stronger mordant than is usually employed can be used withoutdetriment 'to the resist.

In the accompanying drawings, which show one form of apparatus designedto carry into effect this new process of etching, Figure 1 is a sideelevation. Fig. 2 is a plan view. Fig. 3 is a-sectional view on the line3 3 of Fig. 1. Fig. 4 is a vertical section 011 the lineA: 40f Fig. 1.line 5 5 of Fig. 2, and Fig. 6 is a vertical sectional View showing apreferred form of one of the atomizing-nozzles detached.

In the apparatus illustrated there is placed upon a stand an acid-prooftank A for the mordant,which tank has a valved inlet-pipe a and anoutlet-pipe a, the latter being preferably provided with a branch pipeof for the purpose of maintaining a predetermined level of the mordantor etching fluid in the tank. The etching box or chamber 13 rests uponthe bottom of the tank A, said tank having openin'gs through its sidesbelow the normal level of the mordant, so that an air-chamber B,positioned at the bottom of the etching-box, will be submerged in themordant,which will surround the nozzles or atomizersb, which projectfrom the top of the air-chamber. The nozzles or atomizers b each have'acentral passage toithe air-chamber and a plurality of Fig. 5 is alongitudinal section on the impact, which causes each atomized particle1 5c of the mordant to become practically satuducts for the mo lal fithe lower ends of said 100 ducts in use being submerged in the mordant.The openings in the nozzles preferably taper, and above the point ofconvergence the nozzles are recessed, as shown. A suitable distanceabove the nozzles or atomizers the etching-box is constructed to supportslides O, which receive a board,to which the plates prepared for etchingare secured, and attached to the etching-box, adjacent to the openingsthrough which the slides are inserted, are springs c,with whichturn-buttons 0, carried by the slides, may be placed in engagement, andthe etching-box on the opposite side from the springs has sockets orguides, in which are mounted so as to be reciprocated pins 0 The top andsides of the etching-box are preferably transparent, and to carry awaythe fumes and provide for a circulation of air there is attached to theetching-box a ventilating-pipe B Adjacent to the etching-box is awashingcompartment D, the sides thereof having grooves or ledges, sothat the slides may be moved from similar grooves or ledges in theetching-box into the washing-compartment to be positioned over a seriesof perforated pipes D,which are connected to awater-snpply, so thatwater under suitable pressure may be projected upon the plate to removethe mordant therefrom, and to the bottom'of the compartment is secured awaste-pipe d.

To supply compressed air to the air-chamber B and to the nozzlesthereof, an air compressor or pump E is mounted on the stand andconnected to an air-tank E, from which air under compression is taken bya pipe e through a three-way cock f and pipe e to the air-chamber in theetching-box. The cockf is connected to a pipe g,which extends therefromto the upper part of a reservoir G, and to the lower part of the same isattached a pipe h,which communicates with a three-way cock 1;, said cockbeing connected with a water-supply pipe k and to a pipe 7o,which is incommunication with perforated pipes D in the bottom of thewater-compartment. To the pipe 7: is secured a connection or small pipeg, which leads into the pipe 9 just before it enters the tank for thepurpose of preventing the water rising above the upper portion of thepipe 9 and entering the ,pipe g. The several pipes may be provided withcheckvalves to prevent any backtlow of air or water therein. Thethree-way cocks f and t' are provided with handles, which are connectedto each other and to a lever M by a rod m, so that the cocks may beturned in unison.

The cocks are so adjusted that while the cockf is open to let the airpass into the pipe 6 the cock 2 is open to let the water pass from thesupply-pipe 7: through the pipe h to the reservoir G, and when the leveris pulled back the cock f is closed to pipe 6 and open to pipe 9 and thecock 1' is closed to the pipe 7.: and opened to let the water pass fromthe reservoir G tolthe pipe 7t" and thence to the perforated pipes D,the force with which the water is discharged being increased by thepressure of air thereon, the compressed air entering the top of thereservoir through the pipe g when the cock f is turned to cut off thepipe e. Near the air-pump E, to engage with a pulley on thepump-shaft,is mounted a friction-wheel L,and on the shaft which carriessaid friction-wheel is an eccentric disk L, positioned to engage withpins 0 which abut against the slides, and when the disk is turned one ofthe slides C, which has been placed in engagement with the spring 0,attached to the etching-box, will have imparted thereto a reciprocatingmovement which changes the position of the plate to be etched withrespect to the nozzles of the atomizers, so that the greatest dynamicforce and quantity of the atomized mordant will be distributed over thesurface of the plate instead of being concentrated immediately above thenozzles.

In carrying the invention into effect with the apparatus shown the plateis prepared in the usual manner,being coated or covered with a resistexcept where the mordant or etching fluid is to act. The plate orseveral plates to be etched are attached to a board which is placed inthe upper slide, the same being passed into the etching-box, so that theplates will be supported therein face downward. By turning the three-Waycocks compressed air from the air-tank is let into the air-chamber ofthe etching-box and escaping through the nozzles atomizes and projectsthe mordant in the form of spray upon the plates carried by the slide,which is actuated in one direction by the springs and in anotherdirection by the pins which engage therewith, the pins being actuated bythe disk L, to which a rotary motion is imparted.

After the closer lines have been bitten in the plate to the requireddepth the plate is removed from the etching-box and washed, and thelines are then protected by a resistor varnish, after which the boardand plate attached thereto are placed upon the lower slide and againinserted in the etching-box to have the mordant impacted upon the platewith greater force and quantity to deepen therein the wider depressions.

The etching-box is constructed to provide practically a closed chamber,and the boards which carry the plates when placed therein reduce thesize of the chamber, in which the air under compression enters throughthe nozzles to project the mordant, and the air when separated from themordant escapes through the ventilating-pipe, which enters the chamberbeneath the lower slide, said ventilating-pipe carrying away the fumescreated by the chemical action of the mordant on the metal.

\Vhen the slide carrying the plate is moved over or into thewashing-compartinent, the three-way cocks are turned by the lever, sothat compressed airis let into the upper part of the water-chamber togive the requisite pressure to the water therein, so that it may beprojected with force through the perforated pipes and upon the plates,washing the latter free from what-acid may remain thereon.

In some character of work the plate may be etched to a sufficient depthwithout applying other than the original resist thereto, and in suchwork the position of the plate in the etching-box with respect to thedistance from the atomiZing-nozzles may be varied as the etchingproceeds.

In practice the etching fluidis impinged upon the plate in the form of aspray of minute particles, which do not affect that portion of the platewhich is covered by the resist; but where the design on the metal ismore or less broadly exposed the mordant or etching fluid collects andadheres, depending therefrom in the form of spherical drops, which areconstantly being added to by fresh accretions. The mordant which thusadheres to the plate is kept in motion by the impact of new particles ofthe spray and the particles of metal which are removed by the mordantfall to the lower portion of the depending globules, so that theparticles which are removed from the plate fall immediately therefrom.The tendency of a drop of etching fluid or mordant depending from aplate maintained in a horizontal position is to assume a spherical form,and this of itself after the plate has been eroded to such depth as togive elfect to the drops tends to cut a concave or cupped depression,while avoiding lateral erosion or undercutting. Etching by projectingthe mordant in the form of spray upon the metal effects a great gain inrapidity of operation over the methods usually practiced, as a muchstronger etching fluid may be used. The chemical action of the mordantproceeds faster vertically or in the direction of the impact thanotherwise. The impact of the minute particles of the mordant does notdisturb the resist which forms the design, and the heat generated by thechemical action of the mordant upon the plate is absorbed by thecompressed air as it expands,which keeps the mordant, the resist, andthe plate 000]. With the apparatus shown the air which has beenpreviously compressed is allowed to expand and circulate in theetching-box, so that the etching fluid which drops from the plate passesthrough a body of cooled air into the tank from which it was taken, andthe fumes which are given off by the process of etching are carried awayby the ventilating-pipe.

In practice the minute particles of the acid or mordant impingingagainst the plate have their normal force of chemical afflnity enhancedby the force of their impact, which results in each particle of the acidor mordant becoming saturated with the metallic base immediately oncontact with the latter, and the mordant thus loses the power of furtherdissolving the metal; Each succeeding particle impinges in the directionin which the etching is desired to proceed, and the process may besafely continued to a depth beyond which the finer and closer lines ofthe design would become too frail to stand the strain of printing werethe metal undercut.

The rapid decomposition of the metal by the acid develops an amount ofheat which would soon warm the plate to a degree where the resinousresist would soften and give way; but this is prevented by theabsorption of the heat evolved by the expansion of the compressed air inthe chamber, the expansion being sufficient to absorb even more heatthan is developed on the plate, so that the plate and etching liquid iskept quite cool. A further advantage resulting from the use of a chamberor etching-box is that the gases and fumes which are so abundantlygenerated by the rapid chemical decomposition of the metal are carriedoff by the air which escapes through the ventilating-pipe, which pipemay lead to a chimney, and in this way the workroom is kept free fromthese deleterious vapors.

The etching liquid or erodent carried by the blast may of course bevaried for different requirements. In etching copper by means ofiron'chlorid there is a gain of efiiciency as compared with theimmersion method, and in etching zinc with nitric acid the half-tone orcrayon stipple effects are rendered by my process at least as perfectlyas the current methods on copper and there is a great saving of time,apart from the saving in cost of material. IVith a blast of nitric acida halftone etching on zinc can be produced in two minutes, with a purityof the edges of the lines and stipples fully equal to that obtainable oncopper by the immersion method and with a far greater depth of theetching.

In the preparation of a zinc plate for etching the design is produced onthe plate in some fatty ink by the usual photographic process. The plateis then further prepared by first melting into combination with the inkimage some resinous powder to strengthen the image or design against theaction of the acid, the open parts of the design or where the plate isto be etched being left exposed, such steps in the process being such asare usually practiced. My process has to do prin-. cipally with etchingsuch a prepared plate to produce therein indentations, adjacent to whichare the printing-surfaces from which an impression similar to the designcan be made, and it is obvious that the design which has been producedon the plate may be readily destroyed either by abrasion, which wouldremove the resist, or by heat, which would soften or melt the resist.When a plate is etched by the usual means, the depression or lines arenot only cut into the plate vertically, but also sidewise, which resultsin undercutting and in-the production of depressions in the plate, thesurfaces adjacent there to being serrated, or, as it is technicallycalled, rotten.

The apparatus which I have shown is one which may be used forcommercially carrying out the process, and it may be varied in manyparticulars. Forin'stance, where water under sufiicient pressure can behad the water-tank and connections therefrom may be dispensed with.Other means may be used to supply compressed air to the nozzles of theatomizers, and any suitable form of atomizer may be used for projectingthe mordant upon the plate.

1. The process of etching metal plates,within an inclosed space toproduce designs thereon, which consists in atomizing or spraying amordant, by means of compressed air against the face of a plate, havingthereon the design through a resist, so that the dynamic force of theimpact will accelerate the chemical action of the mordan t, and thecompressed air absorb the heat generated by the chemical action of themordant, for the purposes set forth.

2. The process'of etching metal plates, consisting in projecting amordant, in atomized form, upon a plate having thereon a design, whichplate is maintained within an inclosed space, the surface to be etchedbeing substantially at right angles to the direction of projection ofthe mordant, substantially as set forth.

3. The process of etching metal plates, consisting in projecting bymeans of compressed air a mordant in the form of atomized spray upon aplate maintained within an inclosed space, said plate having thereon thedesign to be etched, the mordant being projected upon the plate atsubstantially right angles to its surface, so that the dynamic force ofthe impact will not affect the design, and the heat evolved by theerosive action of the mordant will be absorbed by the air which expandsin the inclosed space, substantially as set forth.

4. The process of etching metal plates, which consists in projectingamordantin the form of spray from a plurality of atomizers upon the plateand moving the plate while under the action of the mordant.

5. The process of etching metal plates by a mordant,which consists inatomizin g or spraying the mordant upon the surface of a prepared plate,moving the plate while it is being etched to change its position withrespect to the atomizers, for the purpose set forth.

6. The process of etching metal plates, con sisting in applying to theplate a prepared design, subjecting it in an inclosed space to theaction of a mordant which is projected upon the plate by air undercompression, the expansion of the air absorbing from the plate andmordant the heat evolved by the erosive action of the mordant inetching, and finally washing the plate, substantially as set forth.

7. The process of etching metal plates having thereon a design inresist, which consists in projecting an atomized erodent against sistingin projectingaliquid erodent or mor-' dant upon a plate maintained in ahorizontal position face downward.

10. The process of etching metal plates bya mordant or acid in liquidform, which consists in atomizing the mordant against the under surfaceof a plate maintained in a horizontal position.

11. The process of etching metal plates, which consists in projecting orspraying a liquid mordant or etching agent upward against a platesupported horizontally in an inclosed space or chamber.

12. The process of etching metal or other plates by a liquid acidsolution or equivalent erodent, which consists in projecting the erodentor acid in the shape of spray upward against and at substantially rightangles to the face of the plate to be etched, said plate beingmaintained in a horizontal position.

13. The process of etching metal plates by a mordant or an acid solutionin liquid form, which consists in projecting the mordant in comminutedform mechanically upward against the under surface of a plate which ismaintained face downward, the mordantso forced against the plate beingpermitted to fall into the body of the solution whence it was taken.

14. The process of etching metal plates by a mordant or acid solutionwhich consists in maintaining a plate inverted in a horizontal positionabove a body of the solution, atomizing and projecting the solution inthe form of spray upward against and in adirection at substantiallyright angles to the surface of the plate to be etched and permitting thesolution so projected against the surface of the plate to fall bygravity or drop into the body of the solution.

15. A step in the process of etching a surface having thereon a resistwhich consists in atomizing by the use of compressed air a mordant uponthe surface maintained in an inclosed space or chamber the expansion ofthe air in said chamber absorbing the heat which arises from chemicalreaction, for the purpose of preventing deterioration or destruction ofthe resist.

16. In an apparatus for etching, the combination of a receptacle havingmeans for maintaining thereina plate in a horizontal posi tion, theplate having a design thereon, atomizers and an acid-tank, for thepurpose set forth.

17. In an apparatus for etching, the combinationof a receptacle orchamber having means for maintaining therein a plate, a plurality ofatomizers projecting from an airsupply toward the plate, an acid-tankadapted to contain acid so as to partially surround the atomizers, andan air-supply in communication with the atomizers, for the purpose set.

forth.

18. In an apparatus for etching, the combination with a chamber oretching-box having means, for maintaining therein a plate, means formoving the plate-support, a plurality of atomizers maintained within anacid-proof tank which contains a liquid erodent so as to project theerodent at right angles to the plate within the chamber, and means as anaircompressor connected with the atomizers for projecting the erodentand reducing the temperature within the chamber so that the heat givenoff by chemical reaction of the erodent upon the metal will be absorbed.

19. In an apparatus for the production of designs or printing-surfacesby etching, the combination with an etching-box having means formaintaining a plate therein, of atomizers, a chamber for compressed airconnected with the atomizers, and a tank for the mordant, for thepurpose set forth.

20. In an apparatus for the production of designs in metal plates byetching, the combination with an etching-box having means for sustainingtherein a plate, a tank for the mordant, an air-chamber within theetchingboX, and means for projecting the mordant against the plate.

21. In an apparatus for the production of etchings, the combination withan etchingbox having a slide to support a plate, openings forintroducing the slide to the etchingbox, and means for reciprocating theslide, of a tank or receptacle for the mordant, a plurality of deviceswithin the etching-box for atomizing or spraying the mordant upward,said devices being arranged at uniform distances apart, and means forconveying air under pressure thereto, substantially as shown.

22. In an apparatus for etching, the combination of an etching-box, amovable platesupport, an acid-proof tank which contains a plurality ofatomizers for projecting a mordant from the tank upon the plate andmeans for moving the plate-support to change its position and theposition of the plate or plates carried therebywith respect to theatomizers.

23. In an apparatus for etching, the combination 'with anetching-box andmeans for projecting a mordant upon a plate positioned therein, of awashing-compartment having means for projecting a fluid, and aplate-carrier which is movable from the etching-box into thewashing-compartment, substantially as shown.

24. In an apparatus for etching, the combination of a tank containingcompressed air, an etching-box or chamber having at its lower portion anacid-proof tank from which project a plurality of atomizers, means foratomizing a mordant by air under compression,

so that the mordant will be projected upon the plate in the form ofcomminuted spray and means for reciprocating the plate in theetching-box, for the purpose set forth.

25. In an etching apparatus,an etching-box having an air-chamberwithatomizers, atank adapted to contain a mordant which surrounds theatomizers, means for compressing air and supplying it through theair-chamber to the atomizers, a plate-carrying slide mounted within theetchingrbox and removabletherefrom, a water-tank in communication. witha water-supply and with the air-compressor, a washing-compartment havingtherein a series of perforated pipes, and cooks for controlling the airand water supply, the parts being organized forcooperation,substantially as shown and for the purpose set forth.

26. In an apparatus for the production of etchings, the combination witha chamber or etching-box having means for sustaining horizontallytherein a plate, a receptacle for etching liquid at the lower part ofthe chamber or etching-box, an air-supply and means connected to theair-supply for projecting the etching liquid upward against the plate.

27. In an apparatus for the product-ion of etchings, the combinationwith a chamber or etching box having means for sustaining therein aplate in a horizontal position, of a tank containing etching liquid, anair-blast, and a device connected with the air-blast by means of whichthe etching liquid may be projected upward against the plate.

28. In an apparatus for the production of etchings, the combination withan acid-proof chamber or etching-box having one or more transparentsides, supports to maintain a plate horizontally within the chamber, anda tank or receptacle for holding a supply of etching liquid, of aplurality of atomizers arranged within the tank and connected with anair-blast by means of which the etching liquid may be projected upwardagainst the plate.

29. In an apparatus for the production of etchings, the combination witha chamber or etching-box having openings and supports for maintaining aplate in a horizontal position, of a tank containing etching liquidpositioned at the base of the chamber, a plurality of atomizers Withinthe tank, means for conveying air under pressure to the atomizers and apipe for conveying gases or fumes from the chamber or etching-box,substantially as shown.

30. In an apparatus for the production of etchings,the combination witha chamber having means for sustaining therein a plate and openings forintroducing the plate into the chamber, of a tank containing etchingliquid, a plurality of devices Within the tank for producing atomizedspray the nozzles of which point upward and are arranged atsubstantially uniform distances apart and a pipe

